text: Silver nanoparticles are thermodynamically unstable in oxic environments. In seawater, silver oxide is not thermodynamically favored when chloride and sulfur are present. On the surface where O is present in much greater quantities than chloride or sulfur, silver reacts to form a silver oxide surface layer. This oxidation has been shown to occur in nanoparticles as well, despite their shell.O in Water:O + HO → 2Ag + 2OH  value of 4×10.  → Ag+ + O → 4Ag + 2O + ½ O + 2H ⇌ 2Ag + H2O  ions are a concern for environmental health, as these ions freely interact with other organic compounds, such as humic acids, and disrupt the normal balance of an ecosystem. These Ag ions will also react with Cl to form complexes such as AgCl, AgCl, and AgCl, which are bioavailable forms of silver that are potentially more toxic to bacteria and fish than silver nanoparticles. The etched structure of silver nanoparticles provides the chloride with the preferred atomic steps for nucleation to occur. + Cl → AgCl + Cl → AgCl  ions will react with HS in the water to form the precipitate AgS.  + HS → AgS + H S is not the only source of sulfur that Ag will readily bind to. Organosulfur compounds, which are produced by aquatic organisms, form extremely stable sulfide complexes with silver. Silver outcompetes other metals for the available sulfide, leading to an overall decrease in bioavailable sulfur in the community. Thus, the formation of AgS limits the amount of bioavailable sulfur and contributes to a reduction in toxicity of silver nanoparticles to nitrifying bacteria.